Full Details from Amazon.com : http://www.amazon.com/gp/product/B0009PEY5S?tag=onigi-20

1GB kit (512MBx2) Upgrade for a Dell Dimension 4600 System (DDR PC3200 NON-ECC CL=3)

184-pin DIMM
DDR400
DDR PC3200 CL3 Unbuffered NON-ECC DDR400 26V 64Meg x 64
The only brand of memory upgrade available directly from a DRAM manufacturer tested to meet the most stringent industry specifications
Install it yourself in about 15 minutes The same top-quality memory that the worlds largest computer manufacturers install in the systems they sell